A stretch of northbound Highway 99 at Avenue 16 is shut down as investigators work to learn more about what caused the accident and clear the wreckage.

Three people were killed in a crash on northbound Highway 99 at Avenue 16. A couple in their 60s and a semi truck driver in his 40s.

According to officers on scene an elderly couple in a motor home made an unsafe lane change -- crashing into a semi carrying sheets of glass. Both then veered right hitting a eucalyptus tree. Both vehicles burst into flames.

CHP officers have been investigating this throughout the night. So far its unknown whether they died from the impact or flames. The flames and smoke were so big that the train stopped blocking Cleveland Avenue -- a major intersection in Madera.

Within the last hour they were able to clear the train tracks and the train is moving. They hope to have at least one lane open by 6 a.m. for the morning commute.

A traffic detour has been set up from Cleveland Avenue to Country Club Drive, to Avenue 17.